Electric clock



A. F. POOLE ELECTRIC CLOCK 'Aug 3, i937.

Filed June 2o, 1935 3 Sheets-Sheet 2 n E V a Aug 37 1937.

5 Sheets-Sheet 5 INVENTOR.

Patented Aug. 3, 1937 UNITED STATES PATENT oFF Arthur F. Poole, Ithacadministrat ceased, assi N.' Y.'

Application June 20, 1933,

ICE

ELECTRIC CLOCK 12 Claims.

My invention is an electric clock of the class whose hands arecontrolled byl a regulated a1- 1,310,372 of 1919.v

One of the objects'of. my

vide improved means to as Wound up by the motor.

fast as` it is being At this' point, the

speed regulator and the hands gearedA thereto are running at synchronousstep yWith the current.

speed and! keep in Another-'object of my invention is to so gear themotorv to the spring whi ch itv winds that the friction of` the gearingconnecting the motor andv spring will prevent the motor from beingpower. ing an outage.

magnet conducting disc grating Watt meter and of my invention to usethis ment for a speed regulator.

So the hands continue to keep time dur- Owing to the characteristic ofthe spring having to unwind as fast as it is being wound by the motor,when a condition of equilibrium has been reached,y power is put in thespring by the spring expends power on therefore said regulatorchronous'speed just as if it to themotor instead of bein must turn atsyn- Were rigidly geared g connected throughIl a, N. Y.; Maryline B.Poole, rix of said Arthur F. Poole, degnor to. Maryline B. Poole,Ithaca,

Serial No. 676,619 (Cl. 58--26) a storage spring. This compensates forany variation-of temperature aiecting the counter torque Whenan outageoccurs the motor stops and the spring unwinds turning the speedregulator and hands geared thereto, since the tension of the springdecreases during the unwinding the speed of the regulator decreases alsoand unless some compensating means were introduced the handsv Would'losetime. It is one of the objects of my invention to provide a change inthe When-the current is resumed after an outage the regulator isturningJ at approximately synchronous speed: under force of the springwhich has-runidown'the amount of the outage. Not having beeny woundduring the outage the spring tension isL correspondingly reduced. Whencurrent is resumed' the motor starts, the spring is changed-athespr-ingwould never reach its original. tensionV` since it is being unwound asfast as it is being Wound. A further object of my inchronous speed hadat the time of the outage. Coincidentally the; counter torque of thespeed regulator is changed to correspondfto the increased tension ofthespring and thus hold the regulator at synchronousl speed. The fact ofthe spring reaching its-original tension determines that the vision of`a placedK from shift shall come into action and also to perform asimilar control for the storage device.

Another object of my invention is in a modification in which the speedregulator is a clock escapement instead of a magnetically braked disc,and the force of the driving or storage spring is used as a measure ofthe length of an outage. Obviously when an outage occurs the tension ofthe driving spring decreases and the amount of such decrease is ameasure of the duration of the outage. When current is resumed it isdesirable to restore the spring to its initial tension, and to that endthe gear ratio of the motor to the spring is changed as explained above.To determine when the tension of the spring has been restored I use theforce of the spring which is being wound. When this tension reaches itsinitial value, the gear shift for the motor is thrown to its normalposition. Thus the storage device is rendered superfluous.

A further modification of my invention is shown in which the gear shiftof the motor is replaced by an electrical change which runs the motor atincreased speed during a rewinding following an outage. The force of thestorage spring is used to determine the speed of the motor. When thespring has been rewound to its initial tension the motor resumessynchronous speed.

A further object of my invention is in the specific mechanisms to carryfunctions. The above and other objects of my invention will be apparentto those skilled in the art as they are set forth in the followingspecication and claims.

My invention may be best understood with the assistance of theaccompanying drawings of whichz Fig. 1 is a perspective view, more orless diagrammatic, of a clock made according to my invention. Figs. 2and 3 are details of certain sections of Fig. 1. Figure 4 is an explodedView and shows a modification in which the force of the driving springreplaces the storage device of Fig. l. Figs. 5, 6, and 'I are details ofFig. 4. Fig. 8 is a view in elevation of a modification in which anelectrical device is used for changing the speed of the synchronousmotor during a period of rewind after an outage, this replacing themechanical gear shift of Figs. 1 and 4. Figs. 10, and 1l are details ofFig. 8, taken on a section through :zt-fc in the direction indicated.Figure 9 is a section taken on Fig. 8 through y-y in the directionindicated. Fig. 12 shows a modification of Fig. 8. Like numbers ofreference refer to the same parts in all the figures.

Referring now to Figs. 1, 10 and 11 are line wires supplied withregulated current as in my patent above referred to. A synchronous motorI2 is connected between the line wires and runs in step with the linecurrent in the wires I and II. A suitable reducing gearing, not shown,reduces the speed of the motor and turns a shaft I3 on which is slidablymounted a pinion I4 held by a keyway I from turning on the shaft I3. Acollar I6 rigid with the pinion I4 has a groove I1 and a finger I8engaging a slot I9 in a pinion loosely mounted on the shaft I3. A jackshaft 2| turns in the frame work and has rigid with it gears 22 and 23,the latter in mesh with the gear 20 and the former adapted to be meshedwith the pinion I4 when the pinion is shifted to an upper position by alever 24 turning on a pivot 25 and having an end 26 engaging the slotI1. A spring 21 holds the lever 24 in a normal position to a stop 28.rhe arrangements are such that when the lever 24 is in its normalposition the gear 20 will turn at the speed of the shaft I3, but whenthe lever 24 is shifted to its alternative position and motion of theshaft I3 is transmitted to the gear 20 through the jack shaft 2l and itsgears 22 and 23, the gear 20 is driven at double the speed in the samedirection. The arrangement just described will be recognized as similarto part of the transmission gears of an automobile. The shifting of thelever 24 is done by means to be described later.

Meshing with the gear 2|) is a gear 29 mounted on a shaft 39 turning inthe frame work. For the purpose of illustration merely and to fix onesideas by definite figures, we will assume that the gear 29, when thelever 24 is in the position shown, turns once a minute. Mounted on thegear 29 is a pinion 3| which drives a wheel 32 on a shaft 33 turning inthe framework. A pinion 34 on said shaft drives a wind wheel 35rotatably mounted on a center shaft 36. The gear ratio between thewheels 29 and the wind wheel 36 is such that the latter turns once anhour.

A spring 31 is attached to the wheel 35 and has its other end fastenedto a drive wheel 33 frictionally mounted on the center shaft 36 on whichis the customary cannon pinion 39 and minute hand 4i). An intermediategear 4I is driven by the pinion 39 and drives an hour wheel 42 on whichis an hour hand 43. The construction is the usual clock one and will beapparent to those skilled in the art from the drawings.

The drive wheel 38 drives a pinion 44 on a shaft turning in the framework and on which is rigidly mounted a wheel 46. The gear ratios aresuch that when the gears 35 and 3B are turning at the same rate theshafts 33 and 45 are turning at the same rate also.

The wheel 46 drives a pinion 41 on a shaft 48 turning in the frame work.The speed regulator is on the shaft 48 and consists of a conducting disc49 mounted on said shaft and turning in the eld of a permanent magnet50. Eddy currents produced in the disc 49 by the ux of the magnet 50retard the motion of the disc in the well known manner and produce acounter torque which regulates the motion of the disc 49. For thepurpose of adjusting this counter torque I have provided a magneticshunt 5I adapted to slide in the frame work 9 by means presently to bedescribed, and thus change the magnetic flux through the disc 49 andconsequently the counter torque.

As thus far described, the motor I2 drives the wind wheel 35 at a speedof one revolution per hour winding the spring 31 at that rate. Sincethere is no slip between the spring 31 and the drive wheel 35 on the onehand and the wind wheel 38` on the other the two wheels must sooner orlater reach the same rate of speed and the hands 49 and 43 then will bemoved as if they were geared directly to the synchronous motor I2. Thiscondition persists so long as the current is on. I will now describe theaction of the device in the event of an outage.

When an outage occurs the mechanism- (a) Keeps track of the length ofthe outage in a storage device;

(b) Changes the counter torque on the disc 49 to compensate for therunning down of the spring 31 so as to keep the disc running atapproximately synchronous speed during the outage.

The storage device consists of a disc 52 on a shaft 53 and having anotch 54 into which may 75 i 61 on the shaft 53'. When the Y ed on theend of a lever lever 92y holds1the hook to` a enter a. feeler 55S on. alever 56'mounted1on a shaft 51 turning in the attached to a wheel 65vmounted on a shaf f liliv turning in the framework. The wheeli 65 is`driven by av pinion are in registry the feeler both: of the samediameter.

The shaft 53 is driven by means of a gear 68 frictionally mounted on theshaft 532 and held against a collar 68" on said shaft-by a slip spring69; a gear shift device is adapted to drive the pivot 14 and held by asspring 15 to a stop 16. The lever 10hastwo yokes 11 and 18 in which arepins 19 and |30-v which engage grooves in the sliding collars 8|-A and82 which are slidably mounted on the shaftsv 45 and 33 respectively. Akeyway 83 in the shaft 45 prevents the collar 8| from turning in respectto the shaft 45 and a keyway 84v in the shaft 33 has alike function forthe collar 82. A gear 85 is on the collar 8|y and isv adapted to meshand turn thegearv 68 when slid on the shaft 45 into the plane of saidgear when the lever 10 is permittedY to'turnto its extreme rightposition. Similarly, the colla-r 82 has asthe gear 86; The reason forthis different ratio will be explained hereinafter.

The normal position ofthe lever 10- is in the central position shown inFigure` 1 where said 1ever is held on the detent 13; When the currentgoes 01T thedetent 13 is unlatched by a hook 89 having a cam. surface 90adapted to contact with a pin 9| in the detent 13. The hook 8'9 ismount- 92 turning on a pivot 93l in the framework andi held bya magnet94 pin the 1ever'92. The magnet 942 mayy have a con- |00 mountedindenser |01' in shunt therewith to prevent; chati-v tering 921 and itsassociated de-energized, the spring 95. moves the lever 92'` in aclockwise direction to a stop 96?', the hook 89. moves to the left andthe cam surface 90.' trips thel detent 13 thus allowing the parts to`vcome into the position shown in Fig..2. In thisy position the gear 85'starts to drive the: gear 68 and displace the storage discs As thespring 31 runs down, the speed regulator would tend to run slower, tocompensate for this decrease in tension I have provided a gear |02 onthe shaft 60' driving a gear |03 on a shaft |04 turning in the frameworkand having mounted thereon a cam. |05 driving a follower |06, mounted ona shaft |01, against a spring |01'. The follower |06 has a fork |08therein which, by a pin |09 in the magnetic shunt 5|, moves said shuntto change the effect of the permanent magnet 50 on the brake` disc 49.The so shaped 'to compensate for the decrease in theV force of thespring 31 and thus keep the disc 49'revolving at approximatelysynchronousspeed, 30

There now remains of events when outage. When netv 94 is made attractsvthe lever 92 to the position shown in Fig. 1. At this time the outagehas lasted long enough in whichy event the notches have not been dis- Ishall discuss (b) first. In this event the lever 56 is in the positionshown in Fig. 1` and is holding a bell crank H04 mounted on a and asurface H5 adapted to act asa stop for said pin. (See 89r is stopped inThe cooper |24 is on an insulating block |251 |26. A conductor |21connects contact |24 to the line wire I I. Thus when the feeler 55 isriding on the circumference of the discs 52 and 60 the contacts |22 and|24 are closed and the magnet ||9 shifts the motor to its double speedposition. This winds the spring 31 at twice the normal speed, once tobalance the motion of the gear 38, which of course is still running, andonce to replace the turns lost during the outage. When the storage discshave been returned to their normal position with the feeler 55 in thenotch 54 the lever 56 breaks the contact springs |22 and |24, the magnet||9 is unmade, the gear shift |4 returns to its normal position, and themotor resumes its normal speed connection. Also the spring 58 turns thebell crank ||0 against the spring IIB, the link I|2 pulls the hookdownward thereby through the pin |I1 releasing the pin 10 engaged by thehook 89 and permitting the lever 10 to return to the position shown inFig. 1 dis-engaging the gear 88 from the idler 81. The parts are now inthe position shown in Fig. l, completing the cycle.

The reason for having the gear 86 half the diameter of the gear 85 isthat when the storage is brought back to normal by the gear 86, thisgear is running at twice the speed at which the storage discs weredisplaced by the gear B5, consequently to bring the discs back in thesame time, corresponding to the double speed of the shaft 33 the gear 86is of half the diameter of the gear 85. To put the matter in anotherway, after an outage, to restore the tension of the spring 31 the shaft33 must make as many turns as made by the shaft 45 during the outageplus the number of turns made by the shaft 45 during the period ofrewind. Since the motor shift is as two to one the shaft 33 turns atdouble speed the length of the rewind. Hence its gear ratio to thestorage must be half that of the shaft 45 to the storage.

As before noted, the object of using the regulator in the form of abrake disc is to avoid the noise of a clock escapement. When this noiseis not objectionable a clock escapement may be substituted for the brakedisc with the advantage of cheapness, since in addition to the saving inthe cost of the permanent magnet, one may omit the device of the gear|03, the cam |05, and their associated mechanism since the variation inrate of a clock escapement with varying motive force is much less thanthat of a brake disc. Further, since the spring 31 is not rewound duringan outage, it is possible, to a rough approximation, to use thevariation in tension of the spring 31 to measure the time the motor |2is to be run at increased speed to restore the initial tension of thespring 31. I have shown an alternative structure to that of Fig. 1 inthese two respects in Figs. 4, 5, 6, and 7.

For the sake of clearness, Figure 4 has been drawn as an exploded View.

Referring now to these figures, a brief description will be all that isnecessary to those skilled in the art on account of the resemblance ofthe alternative structure to that of Fig. 1. As before a synchronousmotor l2 is connected to the mains I0 and |I and is provided with a gearshift similar to that of Fig. l. Through a train of gears 29, 3|, 32,and 34 described before, the motor |2 turns a gear |28 once an hour whenthe motor |2 runs at synchronous speed. Wound by the gear |28 is aspring 31 driving clock hands and 43 and a train of gears as in thestructure shown in Fig. 1. However in the present structure, the gear 46turns a gear |42 on a shaft |43 turning in the framework. A bevel gear|44 on the shaft |43 turns a bevel |45 on a shaft |46 which carries ascape wheel |41 having crown teeth |48. These teeth alternately engageand drive verge arms |40 and on a shaft |5| of a balance |52 whichvibrates under the influence of a spring |53 fastened at one end to theshaft |5| and having the other end attached to the framework 9.

I have used a verge escapement rather than a lever escapement on accountof the fact that the verge will start as Soon as force is applied to it.It is also more sensitive to variations in motive force, a desirablecharacteristic in its present use. When the current is on, a conditionof equilibrium is soon reached between the wheels |28 driven by themotor I2 and the wheel 38 driven by the spring 31, and the wheel 38 willturn as if it were directly geared to the motor |2 and ran in steptherewith.

I shall now describe the means for measuring the tension of the spring31 and controlling the gear shift for the motor |2 therefrom. Referringto Figs. 4, 6, and 7, the spring 31 is' not fastened directly to thegear |28 but is fastened to a pin |30 in an arm |3| turning on the staff|40 which has an upper bearing in a sleeve |4| rigid to the shaft |40and holds the arm |3| between collars |32 and |33, said collars beingalso fast to the shaft |40. The wheel |28 has a slot |29 therein, theends of which limit the rotary motion of the pin |30 which may be heldto one edge of said slot by a spring |36 extending from a pin |34 in thewheel |28. The pin |30 may be drawn to the other edge of said slot |29by the spring 31 fastened to said pin. In the normal running of theclock the spring 31 is stronger than the spring |36. However when thecurrent goes off, the spring 31 runs down and loses its tension,whereupon the spring |36 rotates the arm |3| on the shaft |40 untilstopped by contact of the pin |30 with the edge of the slot |29. Theshaft |40 has a hole therein in which slides a push rod |39 having asmall right angled pin |38 thereon which is guided in an angular slot|31 in the arm |3|. From this results a raising and lowering of the pushrod |39 as the pin |30 goes from one end of the slot |29 to the other inresponse to the pull of the spring 31 or the spring |36 whichever is thestronger.

As so far described, we have the condition that when the clock isrunning under the force of the motor and the spring 31 has its normaltension the push rod |39 is in its upper position, when the current goesoff, the spring 31 runs down, the spring |36 prevails and rotates thearm |3| in a` clockwise direction. The pin |38 is then cammed to itslower position by the slot |36 and the push rod |39 is carried to itslower position also. I will now describe the mechanism by which themotion of the push rod |39 controls the position of the gear shift forthe motor I2.

Referring particularly to Fig. 4 there is a fork |55 on a shift rod |54,said rod sliding on pins |56 and |51 in the framework and being guidedby two slots |58 and |59. The fork |55 engages a slot I1 in the collarpinion I4 which, as pointed out in the description of Fig. l, determineswhether the gear 20 shall revolve 'at synchronous speed or at doublethat speed. In order toshift the rod |54 there is a pin |60 in said rodadapted to be acted on in the arm |3| to a pin |35 I6 and serves toshift the by a slot |6| in a lever |62 turning on a pivot |63 in theframework. The lever |62 has an arm |64 having inclined surfaces |65 and|66 acted on by a roller |61 turning on a pin |68 in a link |69 which is.mounted on a lever |10 on a pivot |1|. Aspring |12 between the lever|69 and the lever in a clockwise lever |62 in one or the other of itsalternative limits the tate the lever |11 in a counterclockwisedirection to a stop but is `prevented from so doing during the .timecurrent is on by the attraction of a magnet |82 connected to the linewires |0 and through la current rectifier |83. A condenser |84 in shuntaround the magnet |82 prevents chattering. The magnet |82 attracts anarmature |8| on the lever 11 and holds said lever to a stop |80. Whenthe the spring l| 19 pulls the lever |11 to the stop |19', the .pin `|16rotates the lever |10 in a counterc'lockwise direction, the roller |61rides over the apex of the angle formed by the surfaces |85 and |66,thelever |62 is thereupon rotated counter-clockwise by the roller |61and the shift rod |54 throws the gear shift 6 to its double speedposition. At this time the motor |2 is stopped since vthere is nocurrent. However things are all `set to have the motor wind the spring31 at When current is resumed, the lever |11 is drawn to the magnet |82.spring 31 is drawn up on resumption detent |86.turns on a shaft having apin |89 therein engaging a fork in the rear end of the detent |86 whichalso is drawn by a spring |90 to the pin |89. The lever |88 is drawn bya spring |9| so that an ear |92 on the .lever |88 ycontacts with thepush rod |39.

tion by the arm |3| rotating in relation to the gear |28. The spring |9|then unlocks the detent |86 and permits the lever |10 to vreturn to itsnormal position under the force of the spring The .roller |61 will thenbe moved to the surface |66 and the gear shift will be thrown to theposition shown in Fig. 4. This completes the cycle.

It is to be noted that the motor to the lines I0 and between the powerhouse and the rectifier |83. Said rectier is of use only to `preventchattering of the magnet 82. The same end may beobtained by omitting therectifier |183 and the condenser |84 and `making the lever |11 of largemoment of inertia.

I2 is connected the spring must not be 'able to drive this 'trainbackwards. This purpose may be accomplished by putting a one-way ratchetsome place in the train.

I have shown a further modiiication of my invention in Fig. 8 withdetails in` Figs. `9, 10, In `this form I have replaced the gear shiftand mechanism for moving the same by an electrical connection in themotor to run it above synchronous speed, and have usedthe force of thedriving spring to determine when this change of speed shall take place.Referring to the above mentioned gures, 200 is a self .startconnected tothe line wires On the motor shaft 20| is a conducting disc 202 whichruns between the poles of an electromagnet 203 having shaded poles V204and a winding 205 adapted to be energized by the 'line current on thewires |0 and as afterwards to be described. The disc 202 and itsassociated magnet 203 form an induction motor and are given -a torquegreater than vthe synchronous torque of the motor 200 so that when thewinding 205 is energized the shaft 20| will be driven at-about two orthree times synchronous speed. The exact ratio, as will afterwardsappear, is not material.

The motor 200 winds a spring by meansv of a worm 206 on the shaft 20|driving a wheel 201 on the axis 208 of which is a second worm 209driving a wheel 2| 0 turning on a shaft 2|| on which is frictionallymounted (to allow the .hands 1 to be eet) a wheel 2|2 driving a pinion213 on a shaft v2|4 on which is a wheel 2|5 driving a pinion 2|6 on ashaft 2|1. The shaft 2|1 carries a speed regulator which I have `shownas a conducting disc 2| 8 revolving in the eld of a permanent magnet 2|9. A clock escapement may be usedas a speed regulator instead of thedisc if the noise is not objectionable.

For the purposes of clearness in the description I have shown theinduction motor 202 as separated from the synchronous motor 200. As amatter of practice, these two motors would `be structure having theabove synchronous speed the winding of the synchronous motor could beopened, thus throwing this motor out of action. The armature would thenspeed up above synchronous speed -due to the unopposed torque of theinduction motor. I consider this latter modification within the scope ofmy invention.

The shaft 2H carries a cannon pinion 220 driving an intermediate gear22| having `a pinion attached thereto turning on a stud 222. The pinionattached to the Wheel 22| drives the hour wheel 223 on a sleeve 224turning on the shaft 2||. The minute hand 226 is carried on the shaft2|| and the hour hand 225 on the sleeve 224. Rigid with the wheel 2|0 isa sleeve or hub 221 turning freely on the shaft 2|| and around this hubis a driving spring 228 fastened at the one end to a stud 229 on thewheel 2|2 and at the other end to a pin230 in an arm 6 23| loose on theshaft 2li. Thus the tension of the spring 288 will tend to rotate thearm 23| in a counterc'lockwise direction (Fig. 10). A spring 232 extendsfrom the arm 23| to a stud 233 in the wheel 2|0 and tends to rotate thearm 23| in a clockwise direction in opposition to the spring 228.Therefore the arm 23| will be in the position shown in Fig. 10 when 228is the stronger and in the position shown in Fig. 11 when the spring 232is stronger. The movement of the arm 23| is delimited by the pin 230 anda slot 234 in the wheel 2|0.

I use the motion of the arm 23| to govern the circuit of the coil 205 bymeans of a snap cam 231 actuated by a spring 235 carried by, andinsulated from the arm 23| by an insulating piece 235'. A hump 236 onthe spring 235 cooperates with the cam 231 mounted on an insulatingcollar 238 which turns on the shaft 2|| freely. The collar 238 has alsomounted on it a slip ring 240 connected by a wire 239 to the cam 231.Insulated banking posts 244 and 245 in the wheel 2|0 serve to limit theangular motion of the cam 231 under the force of the spring 235. It isevident that as the arm 23| is moved from one position to another underthe force of either the spring 221 of the spring 233 the cam 231 will besnapped from the position shown in Fig. 10 to that shown in Fig. 11. Iuse this motion of the cam 231 for closing the circuit of the coil 205of the spring 221. or the spring 233 the cam 231 will which contactswith a spring 24's` mounted on a block 241 on the wheel 2|0 and hencegrounded on the framework. A slip ring 242 is driven on 1 the shaft 2|and has the double function of providing a lower bearing for theinsulating collar 238 and of also taking current from a brush 243connected to the line wire A brush 24| contacting with the slip ring 240is connected to the 40 coil 205 which in turn is connected to the linetension of the spring 228,

wire I0. Therefore the coil circuit is open between the spring 246 andthe cam 231. When the cam is thrown to the position shown in Fig. 1l,which position corresponds to a decreased the coil 205 is closed and themotor 202 runs the motor 200 above synchronous speed. This conditionpersists until the tension of the spring 228 has been restored when thearm 23| is pulled by the tension of the spring 22B against the tensionof the spring 232 to the position shown in Fig. 10 at which time the cam231 is snapped to a position opening the circuit of the induction motor202. The motor 200 then runs at synchronous speed, completing the cycle.

I prefer to make the spring 221 of a large number of turns (the sameapplies to the springs 31 of Figs. 1 and 4) so as to have a smallvariation of the force of said springs in the event of an outage. It isto be borne in mind that outages are of comparatively rare occurrence,and that they are usually short, so that if the clock should get a fewminutes from the correct time during an outage it is no fatal matter, itis only a comparative one between a clock having one error and a clockhaving a larger one. The structure shown in Fig. 1 will give the leasterror due to an outage, that shown in Fig. 4 will give a greater one,and the structure shown in Fig. 8 is the least accurate of all. In eachcase one pays for accuracy by a more complicated structure.

'Io illustrate, suppose the spring 228 has 20 turns and, during anoutage, unwinds one turn per hour. At the end of an hour it has lost veper cent of its force and the disc 2|8 is running ilve per cent slow.The total time lost at the end of an hour is then approximately 21/2 percent of 60 minutes or one and one-hali minutes, an amount 'perfectlysatisfactory for the ordinary household clock. Further, the clock may befurnished with some kind of an outage indicatorthe red indicator on theTelechron clocks shown in a certain patent to Warren will do very wellmand the clock owner has notice to set his clock after an outage if hedesires more accurate time.

In the following claims I have used the word fastened as descriptive ofthe attachment of the driving spring. I Wish this construed as meaningfastened Without slip to distinguish from the prior art in which thereis some kind of slip connection, such as a rictionally attached spring(for example in the patent to Poole, 1,328,247 of 1920), a device tothrow the wind out of action when the spring has reached a certaintension, etc. I believe I am the first to show a non slip connection atboth ends of the driving spring to the end that the clock hands arecompelled to follow the synchronous motor during the time the motor isrunning at synchronism, the spring providing a storage to run the clockduring an outage.

Many changes and modifications may be made in the precise structureherein shown without departing from the spirit of my invention since Iclaimt- 1. In an electric clock adapted to operate from a source ofalternating current of regulated frequency, the combination of asynchronous motor run from said current, a spring, a set of gearswhereby said motor is enabled to wind said spring .5f

at a predetermined rate, a second set of gears whereby said motor isenabled to wind said spring at a predetermined rate which differs inmagnitude from said rst mentioned rate, means responsive to the tensionof said spring, and a gear shift device actuated by said tensionresponsive means for engaging said first set of gears and disengagingsaid second set of gears when the tension of said spring changes apredetermined amount.

2. In an electric clock adapted to operate on a source on alternatingcurrent of regulated frequency, timekeeping means, a spring for drivingsaid timekeeping means, a synchronous motor capable of being operated atsupersynchronous speed, and means responsive to the tension of saidspring for operating said motor at said supersynchronous speed.

3. In an electric clock adapted to operate on a source of alternatingcurrent of regulated irequency, a spring, timekeeping mechanism drivenby and adapted to be rate-responsive to the tension of said spring, asynchronous motor connected to said source of alternating current forwinding said spring, whereby said spring is normally maintained at asubstantially constant tension, means capable of being selectivelydisplaced by the unwinding of said spring and replaced by the winding ofsaid spring, selectively acting means for causing said displacementmeans to be displaced by the unwinding of said spring during aninterruption in said source of current and for causing said displacementmeans to be replaced during the resumption of current fol lowing saidinterruption, and means responsive jointly to the displacement of saiddisplacement means and the resumption of current lor causing said springto be Wound at an accelerated rate.

4. In an electric clock adapted to operate on a source of alternatingcurrent of regulated irequent thereto is approximately equal to thenormal predetermined Winding rate.

5. In an electric motor to Wind said spring.

6. In an electric timing mechanism adapted to type in which the rateincreases with an increase in tension of said spring 7. In an electricclock adapted to operate from an alternating current supply, thecombination of a synchronous motor, a circuit connecting said motor tothe supply, an induction motor having a torque greater than that of saidsynchronous motor, a circuit connecting said induction motor to saidsupply, a spring, means actuated by said motors to Wind said spring, anda contact device operated by the tension of said spring for controllingone of said circuits.

8. In an electric clock adapted to operate from an alternating currentsupply, the combination of a synchronous motor, a circuit connectingsaid motor to the supply, anv induction motor having a torque less thanthat of said synchronous motor,

a circuit connecting said induction motor to the supply, a spring, meansactuated by said motors to wind said spring, and a contact device oper-7 ated vloy the tension of said spring for controlling rst namedcircuits.

9. In an electric clock adaptedto operate'on va source of alternatingcurrent of regulated frequency, the combination of a spring, timekeepingmechanism driven by said springand adapted to be rate responsive tothetension of said spring, timeindicating means of said source of current,whereby said substanappreciable loss of time.

tension of the driving spring increases and being bears an exactpredetermined relation to the frequency of said synchronous speed, andan induction force which source of current when the spring is wound totends to make the rotor run at a speed greater a certain predeterminedtension, a motor mechthan said synchronous speed, and means responanismconnected to said source of alternating sive to the tension of saidspring for controlling 5 current and adapted to wind said spring, saidsaid ie1d,whereby if said tension is less than said 5 motor comprising afield combination and a rotor, predetermined tension by a predeterminedsaid eld combination being so adapted that two amount said inductionforce will predominate forces are brought to bear on said rotor by saidand said rotor run at a greater than synchronous field combination, asynchronous force which speed.

10 tends to make the rotor run at a predetermined ARTHUR F. POOLE. 10

